Abstract
In order to study the effect of KT-30 (N-(2-chloro-4-pyridyl)-N''-phenylurea) treatment on the fruit growth of ‘Monty’ kiwifruit, the changes in some chemical components of the fruit throughout the growing season were investigated, and cell size and starch distribution were observed histochemically. The treatment was done by dipping the flowers into 10ppm KT-30 solution on the 7th d after pollination.
1. The fruit weight increase of the kiwifruit was accelerated with KT-30 treatment by 35-42 d. Weight of the treated fruit was about 1.4 times that of the control on the 170th d after pollination. Some deformity in shape attributable to KT-30 treatment was observed.
2. In the control and treated fruits, starch granules were observed from the 63rd d after pollination in the pericarp, and from the 105th d in the central core by light microscopy. There was no difference in the number of starch granules between the control and treated fruits. There was no change in cell size with KT-30 treatment. It suggested that fruit enlargement with KT-30 treatment was caused by increase of cell number.
3. The analysis of sugar by high-performance liquid chromatography (HPLC) revealed the presence of fructose, glucose and sucrose, and total sugar content in the fruit increased about 1.2 times by KT-30 treatment compared with the control on the 170th d after pollination. This suggested that KT-30 treatment promoted the growth of kiwifruit.
4. As for free organic acids, more citric and quinic acids were found in the treated fruit than in the control, but almost the same pattern was observed in the changes throughout the growing season.
5. Changes in total pectin contents throughout the growing season were similar in both the control and treated fruits, whereas the content was slightly higher in the control. Total pectin was largely composed of hydrochloric acid soluble pectin (HSP) in both control and treated fruits.
6. The pericarp of the control fruit became deep green throughout the growing season, while that of the treated fruit became pale. Chlorophyll content tended to show a higher value in the treated fruit than in the control up to 35 d after pollination, but thereafter it decreased steadily. In the control fruit, however, chlorophyll content tended to increase throughout the growing period. It was supposed that chlorophyll content in kiwifruit was affected by KT-30 treatment.
